Method of coloring metals and product



Patented Apr. 1, 1941 FFICE mnruon or concerns METALS AND raonucr Van M. Dorsey, John S. Thompson, and Edwin W. Goodspeed, Detroit, Mich assignors to Parker Rust=Proot Company, Wayne County, Mich.

No Drawing. Application June 11, 1937,

Serial No. 147,672. Renewed July 5, 1940 7 Claims. (c'i. 148-6) This invention relates to the dyeing and rustproofing of metals, and particularly metals that have had their surfaces treated to form thereon a paint adhering surface. The problem has presented itself of developing a new and improved process for dyeing metal suriaces to provide various colors therefor, and to improve the corrosion resistance as well as the appearance thereof.

In the of small metallic articles, such as machine parts, bolts, nuts, washers, etc, where an inexpensive finish is desired, and where the use of paints and lacquers, etc, is prohibitive, both from an economic standpoint, as well as from more physical considerations such as building up the threads of screws and bolts, a dyeing process, such as herein described, is very advantageous,

' although it should also be understood that much larger objects may be treated Just as satisfactorily.

The principal object of the present invention is to provide a new and improved method of dyeing metal surfaces and to make possible a more economical, uniform and durabl coloring of such articles as well as enhancing their corrosion inhibiting qualities.

A further object is to provide a, new and improved process to improve the corrosion and abrasion resistance of metals and to improve said the Society of Dyers and Colourists, first edition, January 1924, have remarkable corrosion inhibitive properties when applied to metallic surfaces, especially when these surfaces are pretreated in certain ways so as to become more suitable to as phosphates, oxalates or oxides or combinations of these surface treatments. The phosphate treatments especially known as Parkerizlng' and metals in various degrees to take organic dye colors to form a. colored surface.

Another object of the invention is to provide a new and improved method or finishing phosphate, oxalate or oxide coated metal surfaces with a dye and rust-proofing agent to'incrcase their corrosion resistance.

The above and other objects will appear more fully from the following more detailed description.

The present invention relates particularly to a method or process by which the surface of a metal is converted superficially into a non-metallic surf-ace which effectively prevents the formation of corrosion and the immersion of the surface converted metal article into a dyeing solution containing a dye to which has been added a. hexavalent chromium compound. It has been found that a reaction takes place between the dyestufi and the hexavalent chromium compound forming a compound which has been found to be even more superior in corrosion inhibiting qualities than the dye alone. In carrying out the process it has been found that certain dyestufis, such as the Azure Induline and Nigrosine group described as Nos. 859-869 and the Tris A20" dyes described as Nos. 531605, in the color Index or Bonderizing (trade names) have proven to be very advus. .I-t been discovered that these treatments, which are corrosion protective in themselm, are greatly improved by an addirtional treatment in solutions of certain dyestuffs, which dyestufis not only enhance the corrosion inhibiting characteristics of the metal surface, but provide an attractive colored surface which greatly aids the saleabili-ty of the finished article.

As an illustrative example for carrying out the present invention there is set below an example:

' Examples of solutions for forming phosphate coatings:

To gallons ofwater, add: 27. pounds manganese dihydrogen phosphate To 100 gallons of water, add: 27 pounds zinc dihydrogen phosphate The addition of certain oxidizing agents such as sulphites, suiphurous acid, nitrates, nitrites,

chlorcltes, and certain metallic accelerators such as copper may be added to the above solutions to bring about coatings in a much shorter time.

The solution is operated preferably between and 210 F. and the article to be coated is submerged in the solution, or the solution may be sprayed onto the article.

Examples of solutions for forming oxalate coatings:

To 100 gallons of water, add:

40lbs. oxalic acid 8 lbs. sodium nitrate To 100 gallons of water, add: I

40 lbs. oxalic acid 8 lbs. ferric oxalate Example of solution for iorming an oxide coat- Following the converting of the article from a metallic surface to a non-metallic surface. the articles are placed in a wire basket or cage and lowered into a water rinse, the same being kept at a temperature of approximately 200 F. After rinsing for one to two minutes the articles are transferred to the dyeing vat wherein the wire basket is submerged for approximately thirty seconds in a solution comprising one or more of the group of "Azine Induline and Nigrosine, Tris Azo" dyes or mixtures thereof, to which a hexavalent chromium compound has been added. The solution is best operated between 180 and 210 F., but may be used at lower temperatures. Following the dyeing operation, the articles are transferred to a centrifuge and deposited therein and the centrifuge rotated to remove any water present on th work. Oil, preferably linseed, is then sprayed over the articles and the centrifuge is rotated until the articles have dried sufficiently to be handled and packed for use or shipment.

As a specific example of the dye solution, the following is disclosed:

An example using a dye from the Azine Induline and Nigrosine group #859-869:

To 200 gallons of water, add:

50 lbs. Water Black "J #865 lbs. of chromic acid or for convenience a percentage composition of the dye solution is as follows:

, Per cent Water 96.4 Water Black J #865 3.0 Chromic acid 0.6

Per cent Water 96.4 Pontamine Black E Double #581 3.0 Chromic acid 0.6

As a specific example of treating iron and steel, the following is disclosed:

To 100 gallons of water, add:

2'7 pounds of manganese dihydrogen phosphate at a temperature rang-i118 Heat to 210 F. and submerge the article to be treated in the solution until the coating is formed. Following the formation of the phosphate coating, rinse the article with water of approximately 200 F. and apply a dyeing solution made up as follows:

To 100 gallons of water, add:

25 lbs. Water Black J" #865 5 lbs. of chromic acid Temperature 180-210 F. Transfer articles to centrifuge and rotate to remove any excess stain solution present. Spray articles with linseed oil and rotate centrifuge until articles have become dry.

A convenient way of making up a powdered composition to build up such a dye solution is to in the use of a water soluble dye because the basket containing the articles to be dyed may be dipped into the dye from the rinse tank without an intermediate drying operation- A spirit soluble'dye could be used, but it would necessitate an intermediate drying of the work or a removal of all of the water present.

It has been found to be very advantageous to not only coat ferrous metals but non-ferrous metals as well. Very satisfactory phosphate coatings have been obtained on zinc, copper, aluminum and their alloys and these coatings can be finished with the above mentioned dyes for the same purpose as outlined above.

Although there has been described above an immersion process for carrying out the present invention, the process is not limited to this type of application, but the solution may be sprayed onto the metal surface by means of any of the well-known spraying equipment. Following the formation of the phosphate, oxalate or oxide coating on the metal surface the same is subjected to the forced impingement of a water rinse followed by the forced impingement of the dye solution and chromic acid, followed by the forced impingement of oil which may be cut with an organic solvent and the drying of the surface by heat or other well-known means. The articles to be treated may be moved by conveying means through a chamber or the solution may be sprayed on the articles while they are in a stationary position.

There has been disclosed a new and improved process to be used in the dyeing of metal surfaces wherein a rust preventative coating is first formed on the surface of the metal to be treated, followed by the subsequent coloring of the surface of the metal with a dyeing agent to which has been added a hexavalent chromium compound. The process outlined above is inexpensive, easy to apply and when carried out as herein disclosed, provides increased corrosion resistance as well as an attractive color for the surface of the processed article.

We claim:

1. A method of treating metal surfaces selected from the group consisting of iron, steel, zinc, copper and aluminum which consists in forming thereon a coating selected from the group consisting of phosphate, oxalate and oxide and coloring such surface with a tris azo dye.

2. A method of treating metal surfaces selected from the group consisting of iron, steel, zinc, copper and aluminum which consists in forming thereon a coating selected from the group consisting of phosphate, oxalate and oxide and coloring such surface with an azine induline and nigrosine dye of the #859-869 series.

3. A method of treating metal surfaces selected from the group consisting of iron, steel, zinc, copper and aluminum which consists in forming thereon a coating selected from the group consisting of phosphate, oxalate and oxide and coloring such surface with a tris azo dye to which has been added a hexavalent chromium compound.

4. A method of treating metal surfaces selected from the group consisting of iron, steel, zinc, copper and aluminum which consists in forming thereon a coating selected from the group consisting of phosphate, oxalate and oxide and coloring such surface with an azine induline and ni-- grosine dye #859-869 series, to which has been added a hexavalent chromium compound.

5. A method of treating metal surfaces selected from the group consisting of iron, steel, zinc,

copper and aluminum which consists in forming been treated with a tris azo dye to which has been 10 added a hexavalent chromium compound.

7. An'article, the surface of which comprises a coating selected from the group consisting of phosphate, oxalate and oxide, which surface has been treated with an azine induline and nigrosine dye #859-869 series, to which has been added a hexavalent chromium compound.

VAN M. DARBEY. JOHN S. THOMPSON. 

